//when click on the left-menu ul li:
$('#main_title ul li').click(function() {
	//all class are removed
	$('#main_title ul li').removeClass();
	//add class to the selected ul li:
	$(this).addClass("main_title_selected-li");

	//get the selected ul li's name (attribute):
	var s = $(this).attr("name");

	//hide all the right-menu div (profile, resume, etc.)
	$('.main_content').css({
		'display':'none'
	});
	//only display the right-menu div with the same name as name-attribute: 
	$('#'+s).css({
		'display':'block'
	});
});

//set height equal for left and right
$(document).ready(function() {
	var a = $('#main_title ul').height();
	var a1 = $('#main_title ul').width();
	var b = $('#wrap_body_content').width();
	$('.main_content').css({
		'height':a-2*b/100, //18px = 2% width(900px)
		'width':b-a1-2*b/100 //b=900, a1=270
	});
});